1. Field of the Invention
The present invention relates to a damper valve provided in a hydraulic circuit between a hydraulic source and a hydraulic actuator, and a hydraulic power steering apparatus using the same.
2. Description of Related Arts
Provided as a damper valve is a damper valve having a cylindrical casing, a cylindrical partition member for partitioning the casing into two chambers, a communication hole for communicating both end surfaces of the partition member with each other, a valve seat provided on one of the end surfaces of the partition member, a valve plate opposed to the valve seat for covering the communication hole, and a spring for urging the valve plate toward the one end surface of the partition member.
In order to prevent a valve plate from being affixed to a valve seat not to be easily separated therefrom, a damper valve in which a recess communicating with a communication hole is formed in the valve seat has been proposed (see Japanese Unexamined Patent Publication No. 2001-158369 and Japanese Unexamined Patent Publication No. 2004-106642).
However, the valve seat and the valve plate are brought into plane contact with each other, so that oil film cutting easily occurs. Consequently, it is difficult to reliably prevent the valve plate from being affixed to the valve seat. As a result, a steering feeling is liable to be bad.
Therefore, an object of the present invention is to provide a damper valve capable of effectively preventing a valve plate from being affixed to a valve seat and being not easily separated therefrom, and a hydraulic power steering apparatus using the same.